Probably a son of the Rev. Samuel Spalding, Minister of Partoun (1692-1712), and Elisabeth Brown.
Boswell briefly described him as "A drunken laird". 1
Life with Boswell
Boswell either met him at Lord Kenmure's, or possibly just passed on the Lord's description of him.
Unless otherwise noted, the source for a dated quotation of Boswell's is generally the corresponding volume of the Yale Trade Editions of Boswell's journals.